did a compression test....
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From: bay area, CA
did a compression test.... got a 1998 z28 with 167k on the engine.
it would burn massive clouds while driving anywhere. wouldn't cloud up as bad if driven slowly to cruising speed.
starts up one crank everytime.
threw an oil catch can to see if that would help.
finally got around to doing a compression test....
#8 - 135psi #7 - 80psi (90psi with added oil)
#6 - 140psi #5 - 15psi with no change with added oil
#4 - 140psi #3 - 140psi
#2 - 140psi #1 - 140psi
I know kind of an obvious answer, only because I hate to hear it but am I going to need to rebuild the engine?
or can I get away with rebuilding the heads.
thoughts and suggestions encouraged.
it would burn massive clouds while driving anywhere. wouldn't cloud up as bad if driven slowly to cruising speed.
starts up one crank everytime.
threw an oil catch can to see if that would help.
finally got around to doing a compression test....
#8 - 135psi #7 - 80psi (90psi with added oil)
#6 - 140psi #5 - 15psi with no change with added oil
#4 - 140psi #3 - 140psi
#2 - 140psi #1 - 140psi
I know kind of an obvious answer, only because I hate to hear it but am I going to need to rebuild the engine?
or can I get away with rebuilding the heads.
thoughts and suggestions encouraged.
I'd pull the valve cover and both rockers on suspect cylinder. Then hook up compressed air to that cylinder through spark plug hole. This will seat both valve and you'll be able to hear where your problem is by where you can hear the air escaping. You'll hear it in either the intake, exhaust manifold or crank case.
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Number 5 and 7 are notorious for breaking ring lands cracking etc..........I'm sure you can guess the rest. Ask me how I know? Does it knock cold? Seriously with those numbers I would yank the heads, inspect the pistons. You'll see the damage easily with the heads off.
Last edited by RockinWs6; Oct 29, 2016 at 11:57 PM.
Thread Starter
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From: bay area, CA
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Verdad Gallardo TECH Addict
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You can change the pistons easily, just buy a couple used ones and stuff um back in the holes. As long as the cylinders aren't too effed up. Gotta have some experience to to call what will make it though....I bean down this road a few times.
Get a cheapo $10 borescope on ebay and look down in the suspect cylinders. Sounds like you pinched a ring or something. Harbor freight has a nicer one but it costs more as well.
http://www.ebay.com/itm/5M-4LED-Endo...-/172318166104
http://www.ebay.com/itm/5M-4LED-Endo...-/172318166104
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Number 5 & 7 says it all......I seriously doubt a blown gasket etc. The rings and piston overheat, ring expands too much and has to go some place. At the same time the very top edge of the piston is overheated, ring land + ring breaks and this can happen FAST! Leak down test will show all and a bore scope would tell some BUTT.................sometimes its just OBVIOUS its time to tear down.
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From: St.Charles MO
Number 5 and 7 are notorious for breaking ring lands cracking etc..........I'm sure you can guess the rest. Ask me how I know? Does it knock cold? Seriously with those numbers I would yank the heads, inspect the pistons. You'll see the damage easily with the heads off.
Although you may not be able to tell just with the heads off. My #5 piston looked ok from the top until i took it out and the ring was two pieces and and a little piece of ringland fell off.
Hate to say it OP but you probably need a tear down.
Edit: also mine never smoked, knocked or anything. Just showed up as a missfire on #5. In the low rpms you could tell, it would kinda sputter and buck.